Dina Rudick / Globe Staff

The crowd chanted "it's not that cold" before racing into the water at Dorchester Bay for the annual L Street Brownies Polar Bear Swim.

Dina Rudick / Globe Staff

Participants take the frigid plunge for fun and to raise money for a variety of causes.

Dina Rudick / Globe Staff

The swim is sponsored by the City of Boston, Boston Centers for Youth and Families, Curley Community Center, and the L Street Brownies.

Dina Rudick / Globe Staff

Creative outfits were plentiful at the plunge.

Dina Rudick / Globe Staff

Some swimmers wore more covering than others.

Dina Rudick / Globe Staff

The water temperature was just over 40 degrees.

Dina Rudick / Globe Staff

The event derives from a Northern European tradition and was exported to South Boston in 1901.